[mips][microMIPSr6] Implement initial subtarget support

[jkolek]

Summary

This patch introduces microMIPSr6 as a subtarget.

[dsanders]

LGTM with a couple nits.

lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp

134

Do we need to check both here? I'd expect isMicroMips(STI) to be true for all revisions of microMIPS like the way hasMips32() is true when Mips32r6() is true.

lib/Target/Mips/MipsInstrInfo.td

186

Nit: indentation

[jkolek]

In this patch the feature FeatureMicroMips32r6 is removed, isMicroMips(STI) is true for both mips32r2 and mips32r6. The type of microMIPS is determined according to processor which can be mips32r2 or mips32r6.

[zoran.jovanovic]

LGTM.

lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.h

 class MipsMCCodeEmitter : public MCCodeEmitter {
   MipsMCCodeEmitter(const MipsMCCodeEmitter &) = delete;
   void operator=(const MipsMCCodeEmitter &) = delete;
   const MCInstrInfo &MCII;
   MCContext &Ctx;
   bool IsLittleEndian;
 
   bool isMicroMips(const MCSubtargetInfo &STI) const;
+  bool isMips32r6(const MCSubtargetInfo &STI) const;
 
 public:
   MipsMCCodeEmitter(const MCInstrInfo &mcii, MCContext &Ctx_, bool IsLittle)
       : MCII(mcii), Ctx(Ctx_), IsLittleEndian(IsLittle) {}
 
   ~MipsMCCodeEmitter() {}
 
   void EmitByte(unsigned char C, raw_ostream &OS) const;

lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp

static void LowerDextDins(MCInst& InstIn) {
   InstIn.setOpcode((Opcode == Mips::DEXT) ? Mips::DEXTM : Mips::DINSM);
   return;
 }
 
 bool MipsMCCodeEmitter::isMicroMips(const MCSubtargetInfo &STI) const {
   return STI.getFeatureBits() & Mips::FeatureMicroMips;
 }
 
+bool MipsMCCodeEmitter::isMips32r6(const MCSubtargetInfo &STI) const {
+  return STI.getFeatureBits() & Mips::FeatureMips32r6;
+}
+
 void MipsMCCodeEmitter::EmitByte(unsigned char C, raw_ostream &OS) const {
   OS << (char)C;
 }
 
 void MipsMCCodeEmitter::EmitInstruction(uint64_t Val, unsigned Size,
                                         const MCSubtargetInfo &STI,
                                         raw_ostream &OS) const {
   // Output the instruction encoding in little endian byte order.
   // Little-endian byte ordering:
   //   mips32r2:   4 | 3 | 2 | 1
   //   microMIPS:  2 | 1 | 4 | 3
   if (IsLittleEndian && Size == 4 && isMicroMips(STI)) {
     EmitInstruction(Val >> 16, 2, STI, OS);
     EmitInstruction(Val, 2, STI, OS);
   } else {
     for (unsigned i = 0; i < Size; ++i) {
       unsigned Shift = IsLittleEndian ? i * 8 : (Size - 1 - i) * 8;
       EmitByte((Val >> Shift) & 0xff, OS);
     }
   }
 }

lib/Target/Mips/MipsInstrInfo.td

 def HasMips64    :    Predicate<"Subtarget->hasMips64()">,
                       AssemblerPredicate<"FeatureMips64">;
 def HasMips64r2  :    Predicate<"Subtarget->hasMips64r2()">,
                       AssemblerPredicate<"FeatureMips64r2">;
 def HasMips64r6  :    Predicate<"Subtarget->hasMips64r6()">,
                       AssemblerPredicate<"FeatureMips64r6">;
 def NotMips64r6  :    Predicate<"!Subtarget->hasMips64r6()">,
                       AssemblerPredicate<"!FeatureMips64r6">;
+def HasMicroMips32r6 : Predicate<"Subtarget->inMicroMips32r6Mode()">,
+                       AssemblerPredicate<"FeatureMicroMips,FeatureMips32r6">;
 def InMips16Mode :    Predicate<"Subtarget->inMips16Mode()">,
                       AssemblerPredicate<"FeatureMips16">;
 def HasCnMips    :    Predicate<"Subtarget->hasCnMips()">,
                       AssemblerPredicate<"FeatureCnMips">;
 def RelocStatic :     Predicate<"TM.getRelocationModel() == Reloc::Static">,
                       AssemblerPredicate<"FeatureMips32">;
 def RelocPIC    :     Predicate<"TM.getRelocationModel() == Reloc::PIC_">,
                       AssemblerPredicate<"FeatureMips32">;

 }
 class ISA_MIPS64   { list<Predicate> InsnPredicates = [HasMips64]; }
 class ISA_MIPS64_NOT_64R6 {
   list<Predicate> InsnPredicates = [HasMips64, NotMips64r6];
 }
 class ISA_MIPS64R2 { list<Predicate> InsnPredicates = [HasMips64r2]; }
 class ISA_MIPS32R6 { list<Predicate> InsnPredicates = [HasMips32r6]; }
 class ISA_MIPS64R6 { list<Predicate> InsnPredicates = [HasMips64r6]; }
+class ISA_MICROMIPS32R6 {
+  list<Predicate> InsnPredicates = [HasMicroMips32r6];
+}
 
 // The portions of MIPS-III that were also added to MIPS32
 class INSN_MIPS3_32 { list<Predicate> InsnPredicates = [HasMips3_32]; }
 
 // The portions of MIPS-III that were also added to MIPS32 but were removed in
 // MIPS32r6 and MIPS64r6.
 class INSN_MIPS3_32_NOT_32R6_64R6 {
   list<Predicate> InsnPredicates = [HasMips3_32, NotMips32r6, NotMips64r6];

lib/Target/Mips/MipsSubtarget.h

public:
   // Hard float for mips16 means essentially to compile as soft float
   // but to use a runtime library for soft float that is written with
   // native mips32 floating point instructions (those runtime routines
   // run in mips32 hard float mode).
   bool inMips16HardFloat() const {
     return inMips16Mode() && InMips16HardFloat;
   }
   bool inMicroMipsMode() const { return InMicroMipsMode; }
+  bool inMicroMips32r6Mode() const { return InMicroMipsMode && hasMips32r6(); }
   bool hasDSP() const { return HasDSP; }
   bool hasDSPR2() const { return HasDSPR2; }
   bool hasMSA() const { return HasMSA; }
   bool useSmallSection() const { return UseSmallSection; }
 
   bool hasStandardEncoding() const { return !inMips16Mode(); }
 
   bool abiUsesSoftFloat() const;